Blue Light Photobiomodulation

ABSTRACT

The invention is directed to a light source device ( 10 ) comprising a light emitting element ( 12 ) for emitting a blue light having a wavelength ranging from 435 to 500 nm, the light source device ( 10 ) being configured to provide the blue light to at least one cell (C) at a transmitted fluence ranging from 0.01 to 18. J/cm 2  to promote or induce growth and proliferation of the cell (C) and wherein the light emitting element ( 12 ) has a power density ranging from 0.05 to 30 mW/cm 2 . The invention is also directed to a light source assembly comprising a product adapted to be in contact with the skin or a wound and a light source device ( 10 ) connected to the product for providing blue light to at least one skin cell (C), preferably of the wound.

TECHNICAL FIELD

This invention relates to a light source device able to promote orinduce growth and proliferation of skin cells, notably for the treatmentof wounds and injuries, through a photobiomodulation mean. The inventionalso relates to a light source assembly comprising such a light sourcedevice.

BACKGROUND OF THE INVENTION

Healing of a wound is a natural physiopathological process, the humanand animal tissues being able to repair lesions by specific processes ofreparation and regeneration.

Natural healing of a wound proceeds mainly according to three majorchronological sequences. Each one of these sequences is characterized byspecific cellular activities and is controlled by a multiplicity ofsignals of regulation (as well as positive and negative) which,collectively, orchestrate and frame the progression of the process ofrepair. One distinguishes as follows:

-   -   the inflammatory phase;    -   the phase of proliferation (which includes the phase of        granulation and epithelialization; and    -   the phase of remodeling.

The first phase, also called the inflammatory phase, begins since therupture from the blood-vessels, event which starts the formation of aclot (coagulation of blood) mainly made up of fibrin and fibronectin,and which will constitute a provisional matrix. This matrix fills thelesion partly and will allow the migration, within the injured zone, ofinflammatory cells recruited to ensure the debridement of the wound.This phase is characterized by the infiltration on the site of thelesion, of many inflammatory cells (polynuclear, macrophages) ensuringthe defense of the organization against possible foreign micro-organismsas well as the cleaning of the wound or debridement.

The second phase corresponds to the development of the granulationtissue. One observes initially a colonization of the wound by migrationand proliferation of the fibroblasts. Then, the migration of endothelialcells starting from the healthy vessels will allow theneovascularization, or angiogenesis, of the injured tissue. In thegranulation tissue, the fibroblasts are activated and will bedifferentiate into myofibroblasts that present important contractileproperties. These properties are generated by the actin microfilamentsthat thus allow a contraction of the wound. These myofibroblasts play amain function in the formation and the contraction of granulation tissuewhich will lead to the healing of the lesion. There is then migration ofthe keratinocytes starting from the edges of the wound, leading to therebuilding of the skin.

This phase of development of the granulation tissue is initiatedfollowing a preliminary reduction in the general inflammatory state ofthe lesion, with the progressive disappearance of polynuclear and theappearance of macrophages.

Nevertheless, certain types of wounds do not heal correctly, the 3 keystages of the process described previously turned in an abnormal way.Indeed the speed and the quality of the healing of a wound depend onintrinsic and extrinsic factors. This process of repair can thus beabnormally prolonged according to:

-   -   etiology of the wound;    -   its state and its localization;    -   occurrence of an infection caused by the presence of certain        infectious agent like Staphylococcus aureus or Pseudomonas        aeruginosa; the existence of a preexistent pathology (like the        diabetes, an immunizing deficiency, a venous insufficiency,        etc);    -   external environment; or genetic factors predisposing or not        with disorders of the wound healing.

To enhance the process of wound healing, for both wounds which healnaturally and chronic wounds, it is known from the art to usephototherapy. Two types of phototherapies are known, the photodynamictherapy and the photobiomodulation.

Photodynamic therapy is a method that uses a photosensitizer, orphotosensitizing agent, which is disposed or injected near skin or woundcells and activated by a light of a specific wavelength.Photosensitizers have the ability to interact with the nearby skin cellswhen exposed to a light with a specific wavelength. Photodynamic therapyis thus an indirect phototherapy because the light is provided to thephotosensitizer to treat the skin cells, not directly to the skin cells.

Photobiomodulation is a method allowing to have a biological effect onskin or wound cells directly, which means without the need of anyprovisional product or composition to transpose or potentialize anybiological effect engendered by the light source. This method can bedistinguished from the photodynamic therapy which needs absolutely andevery time the intervention of an intermediate product (photosensitizeror a photosensitizing agent) between the light source and the cells topotentialize the biological effect of the light on cells. In otherwords, in photobiomodulation, light has a direct effect on cellswhereas, in photodynamic therapy, light has an indirect effect on cellsvia the activated photosensitizer. As mentioned in the technical fieldabove, the present invention is directed to photobiomodulation.

Furthermore, in phototherapy, it is well known to determine thewavelength of the light to be provided depending on the type of effectthat is expected on the skin cells. Particularly, light having awavelength between 435 and 500 nm (blue light) has antibacterial effectsand also act on human cells. [Ashkenazi H., Malik Z., Harth Y., NitzanY., Eradication of Propionibacterium acnes by its endogenic porphyrinsafter illumination with high intensity blue light. FEMS Immunology andMedical Microbiology 2003, 35:17-24].

More particularly, it was shown that blue light irradiation enables toinhibit the proliferation and migration of skin cells [Taflinski, L,Demir, E, Kauczok, J, Fuchs, P C, Born, M, Suschek, C V, Oplander, C:Blue light inhibits transforming growth factor-beta1-inducedmyofibroblast differentiation of human dermal fibroblasts. Experimentaldermatology 2014, 23: 240-246] and [Mamalis A., Garcha M., Jagdeo J.Light Emitting Diode-Generated Blue Light Modulates FibrosisCharacteristics: Fibroblast Proliferation, Migration Speed, and ReactiveOxygen Species Generation Lasers in Surgery and Medicine 201547:210-215]. It is also well known that inhibiting the proliferation ofskin cells can be useful to enhance the phase of remodeling during woundhealing.

As an example of the effect of blue light, document US-A-2014/0277293 isdirected to the use of LED generated low-level light therapy. Tests showthat light emitting diode having a dominant emission wavelength of 415nm, wavelength comprised between 385 and 445 nm, and providing aneffective fluence comprised between 0 and 35 J/cm² during many definedirradiation times which means that the irradiance of the light sourceused is of 43 mW/cm², allows to inhibit fibroblast proliferation. Thisdocument thus supports the fact that blue light emission is generallyknown as an inhibitor of the proliferation of specific types of skincells.

It should be noted that toxicity occurs for shorter and dominantemission wavelengths of blue light between 410 and 420 nm [Oplander, C,Hidding, S, Werners, F B, Born, M, Pallua, N, Suschek, C V: Effects ofblue light irradiation on human dermal fibroblasts. Journal ofphotochemistry and photobiology B, Biology 2011, 103: 118-125].Therefore, the blue light emission with a dominant emission wavelengthof 415 nm disclosed in the method of US-A-2014/0277293 might be toxic.

SUMMARY OF THE INVENTION

It was surprisingly discovered that irradiating cells with blue lightunder specific conditions can have an unexpected technical effectconsisting in promoting or inducing growth and proliferation ofirradiated cells. Indeed, this is particularly unexpected because bluelight is generally known for anti-proliferation effect whereas theseexperimentations showed that blue irradiation under specific conditionsenables to have proliferation effect, preferably at specific dominantemission wavelength, irradiance and/or fluence.

Proliferation effect is particularly advantageous to enhance the phaseof proliferation during wound healing. Indeed, inducing a proliferationeffect during the phase of proliferation and granulation is the key toenhance the wound healing process.

Furthermore, irradiating cells of a wound with blue light enables tobenefit from all the known effects of blue light, such as antibacterialand anti-inflammatory effects, in addition to the unexpectedproliferation effect.

The unexpected technical effect is achieved with a light source devicecomprising a light emitting element for emitting a blue light having awavelength ranging from 435 to 500 nm, the light source device beingconfigured to provide the blue light to at least one cell (C) at atransmitted fluence ranging from 0.01 to 18.5 J/cm² to promote or inducegrowth and proliferation of the cell (C) and wherein the light emittingelement (12) has a power density ranging from 0.05 to 30 mW/cm².

According to an embodiment of the light source device, the cell isselected from a skin cell.

According to another embodiment, skin cells are keratinocytes orfibroblasts.

According to another embodiment, the dominant emission wavelength rangesfrom 450 to 490 nm, more particularly from 450 to 460 nm.

According to another embodiment, the light source device is configuredto provide the blue light at a transmitted fluence so that the cellreceives an effective fluence ranging from 0.01 to 10 J/cm².

According to another embodiment, the light emitting element has a powerdensity ranging from 20 to 25 mW/cm², and preferably of 23 mW/cm².

According to another embodiment, said light emitting element comprisesat least one LED.

According to another embodiment, the light source device comprises apower source providing electrical power to said light emitting element.

According to another embodiment, said power source is a battery.

According to another embodiment, the light source device comprises atleast one among a microchip processor, a control unit, a communicationunit, an external port and a sensor.

It is another object of the invention to provide a light source assemblycomprising a product adapted to be in contact with the skin or a woundand a light source device as described above connected to the productfor providing blue light to at least one skin cell, preferably of thewound.

According to an embodiment of the light source assembly, the product isone among a dressing, a strip, a compression means, a band-aid, a patch,a gel, a film-forming composition and a rigid or flexible support,preferably a dressing.

According to another embodiment, the dressing comprises at least ahydrocolloid or an adhesive layer in contact with the skin or the wound.

According to another embodiment, the light source assembly is adapted todispose the light emitting element in a position wherein the lightemitting element is facing the skin, preferably facing a wound formed onthe skin.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 represents in a cross section view an embodiment of aphotobiomodulation device used in the treatment of various skinconditions or for promoting or inducing growth and proliferation ofcells in vitro or in vivo.

FIG. 2 is a schematic representation showing the keratinocyteproliferation, 24 hours after different energy densities with blue lightirradiation (transmitted fluence in J/cm²).

FIG. 3 is a zoom of FIG. 2 in the transmitted fluence range of 0.01 to30 J/cm².

FIG. 4 is a schematic representation showing the fibroblastproliferation, 24 hours after different energy densities with blue lightirradiation (transmitted fluence in J/cm²).

DETAILED DESCRIPTION

The present invention will be described below relative to severalspecific embodiments. Those skilled in the art will appreciate that thepresent invention may be implemented in a number of differentapplications and embodiments and is not specifically limited in itsapplication to the particular embodiment depicted herein.

For the purpose of the present invention, the following terms aredefined.

The term “Wavelength” is the distance between two peaks of a wave. Thesymbol for wavelength is λ (lambda) and the unit of measurement isnanometers (nm).

The term “Dominant emission wavelength” is the wavelength or a narrowrange of wavelengths the light source emits the majority of the time.The term “power” refers to the rate at which work is perform; the unitof power is Watt (W) and since the light output power is low it isexpressed in milliwatts (mW).

The term “power density” or “light intensity”, or “irradiance”, or“exitance” is the power divided by the area of the target beingilluminated by the light and is expressed in mW/cm².

The term “fluence” or “energy density” or “dose” expressed in Joules percm² (J/cm²) is the product of power (mW) and time per spot size (cm²).

The term “photobiomodulation” is the ability of the light source deviceto have a biological effect on cells, in particular on skin cells,directly, which means without the need of any provisional product orcomposition to transpose or potentialize any biological effectengendered by the light source. This term can be distinguished from theterm of “photodynamic therapy” which needs absolutely and every time theintervention of an intermediate product between the light source and thecells to potentialize the biological effect of the light on cells.

A first object of the invention is a light source device comprising alight emitting element for emitting a blue light having a wavelengthranging from 435 to 500 nm, the light source device being configured toprovide the blue light to at least one cell (C) at a transmitted fluenceranging from 0.01 to 18.5 J/cm² to promote or induce growth andproliferation of the cell (C) and wherein the light emitting element(12) has a power density ranging from 0.05 to 30 mW/cm².

According to FIG. 1, a light source device 10 comprising a lightemitting element 12 for emitting a blue light having a wavelengthranging from 435 to 500 nm is proposed. The light source device 10 isable to emit light at wavelengths within the range of 435 to 500 nm,preferably within a specific dominant emission wavelength of 450-490 nmand preferably within a specific dominant emission wavelength of 450-460nm. More particularly, the chosen dominant emission wavelength may be453 nm. It should be noted that emitting light at wavelengths within therange of 435 to 500 nm allows blue light emission not to be toxic,contrary to the chosen blue light wavelength range of US-A-2014/0277293,because of most of the emitted wavelengths are comprised in anotherdominant emission wavelength.

Furthermore, the light source device 10 is configured to provide bluelight to cells C at an irradiance and a fluence (dose or energy density)able to promote or induce growth and proliferation of cells C. Thefluence at which blue light is provided to the cells C corresponds tothe specific conditions, particularly specific condition of irradianceand exposition with a light source having a specific dominant emissionwavelength; allowing to obtain the unexpected technical effect withregard to the prior art, such as US-A-2014/0277293. Indeed, it wasobserved that monitoring the irradiance of the provided blue lightallows to have proliferation effect so that growth and proliferation ofirradiated cells are promoted or induced. Particularly, it was observedthat blue light irradiation have a proliferation effect on keratinocytesand fibroblasts.

It seems that the key notions of dominant emission wavelength and/orirradiance give a particular benefit to the unexpected proliferativeeffect on keratinocytes and fibroblasts from skin wound.

Experimentation showed that proliferation effect may be obtained thanksto the action of blue light irradiation on cell pathways. Indeed, it wasobserved that providing the cells C with blue light induces adownregulation or an upregulation of different pathways. Particularly,the TGF-BETA signaling pathway (KEGGID: 4350) is downregulated. Thispathway leads to the differentiation of fibroblasts. Therefore, reducingfibroblast's differentiation explain the activation of the proliferation(because the 2 functions are opposite in cells behavior). On thecontrary, ErbB signaling pathway is activated, explaining the increaseof the fibroblast, as EGF has been linked to their proliferation. [Yu etal. Effect of EGF and bFGF on fibroblast proliferation and angiogeniccytokine production from cultured dermal substitutes. J Biomater SciPolym Ed. 2012; 23(10):1315-24].

The growth and proliferation of cells, preferably skin cells, may beperformed in vitro or in vivo. Indeed, cells may be in culture or may becells of a tissue, preferably a mammal tissue.

The light source device 10 may be configured to provide light at aspecific fluence to a mammal skin tissue or to in vitro cells to providethe proliferation effect. Thus, the light source device 10 isparticularly useful in wound healing. According to this embodiment, thelight source device transmits the blue light onto the surface of awound.

Depending on many interference means, as described above, disposedbetween the cells and the light source, the effective fluence of theblue light received by the skin cells may be lower than the fluencetransmitted by the light emitting element. Indeed, it was also observedthat a larger fluence has to be generally transmitted by the lightemitting element 12 to provide a predetermined fluence of blue light toskin cells C, i.e. an effective fluence of blue light adsorbed by cells.Indeed, during the emission, a part of the blue light is adsorbed byother elements than skin cells C which induces a loss of blue light.Therefore, the light source device 10 is configured to provide bluelight at a transmitted fluence so that the skin cells C receive apredetermined fluence or an effective fluence. Depending on the elementsthat can be present between the light emitting element and the targetcells, the attenuation or absorption effect of the light may lead to anattenuation ranging from 20% to 60% or from 30% to 50% of the energydensity, particularly around 45%.

To obtain the unexpected proliferation effect with skin cells,preferably with keratinocytes, the irradiance or power density is in therange of about 0.05 mW/cm² to about 30 mW/cm², particularly 0.1 mW/cm²to 1 mW/cm², 1 mW/cm² to about 2 mW/cm², 2 mW/cm² to 5 mW/cm², 5 mW/cm²to 10 mW/cm², 15 mW/cm² to 25 mW/cm² or any irradiance in a rangebounded by, or between, any of these values. The power density used totreat target cells or target tissue is of 0.05 to 30 mW/cm², preferablyof 15 to 25 mW/cm², preferably of 20 to 25 mW/cm² and more particularlyof 23 mW/cm².

The effective dose or fluence received by skin cells, in particular of awound or a given surface of skin tissue, may be about 0.01 J/cm² toabout 0.1 J/cm², or about 0.1 J/cm² to about 10 J/cm², or about 1 J/cm²to about 2 J/cm², or about 2 J/cm² to about 3 J/cm², about 3 J/cm² toabout 4 J/cm², or about 4 J/cm² to about 5 J/cm², or about 5 J/cm² toabout 6 J/cm², or about 6 J/cm² to about 7 J/cm², or about 7 J/cm² toabout 8 J/cm², or about 8 J/cm² to about 9 J/cm², or about 9 J/cm² toabout 10 J/cm², or any light dose in a range bounded by, or between, anyof these values. Preferably, the effective fluence used to treat targetcells or target skin tissue is of about 0.01 J/cm² to about 10 J/cm².

As indicated above, the fluence (dose or energy density) notably dependson both irradiance (mW/cm²) and time. Therefore, obtaining thepredetermined fluence may be accomplished by using a higher power lightsource, which may provide the needed energy in a shorter period of time,or a lower power light source may be used for a longer period of time.Thus, a longer exposure to the light may allow a lower power lightsource to be used, while a higher power light source may allow thetreatment to be done in a shorter time.

The duration of radiation or light exposure administered to a skintissue or a culture of skin cells, such as keratinocytes, may also vary.In some embodiments, the exposure ranges from at least 1 second, atleast few seconds, or at least 1 minute, or at least 2, 3, 4, 5, 6, 7,8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 minutes; or up to about1 hour or, for any amount of time in a range bounded by, or between, anyof these values.

According to a specific embodiment, the light source device is used inthe growth and proliferation of dermis cells, in particular offibroblasts under specific conditions. Particularly, it was observedthat proliferation effect occurs on fibroblasts when provided with aneffective fluence of about 6 J/cm² with a power density of about 23mW/cm² during about 7.5 minutes. Similarly, it was observed thatproliferation effect occurs on keratinocytes when provided with aneffective fluence of about 1 to 10 J/cm² with a power density of about23 mW/cm² during about 7.5 minutes

For thermal issues, light source device may be configured to irradiatecells either continuously or in pulses. Indeed, pulsed light irradiationwill typically be preferred than continuous light if there are somethermal issues; indeed, light source provides heating. The decisionwhether to use constant irradiation of pulsed light irradiation dependson the exact application and on the total desired irradiation. When thelight exposure depends on the duration of a pulsed light, the net lighttime may be determined by the sum of the duration of each pulse.

The light emitting element 12 is a device able to performphotobiomodulation. An example of such a light emitting element 12 is alight-emitting diode (LED or OLED, preferably LED) or a lamp which isable to emit light at wavelengths within the ranges of 435 to 500 nm andhaving preferably a dominant emission wavelength comprised between450-460 nm, as well as at a dominant emission wavelength of 453 nm. Inthe embodiment shown on FIG. 1, the light emitting element 12 comprisesthree light-emitting diodes. Alternatively, the light emitting element12 may comprise one or more light-emitting diode (or lamp) able to emita blue light having a wavelength ranging from 435 to 500 nm, havingpreferably a dominant emission wavelength comprised between 450 to 460nm or having a dominant emission wavelength of about 453 nm.

For supplying electricity to the light emitting element 12, the lightsource device 10 may comprise a power source connected to the lightemitting element 12. The power source may comprise an electric cable toconnect to a power grid. Alternatively, the power source may be abattery. The light source device 10 is compact and able to communicatewith a smartphone or a tablet thanks to a wireless communicationprotocol (Bluetooth or Bluetooth smart or Bluetooth Low Energy,preferably Bluetooth Low Energy).

For controlling the light emitting element 12, the light source device10 may comprise at least one among a LED Driver, a sensor, a microchipprocessor, a control unit, a communication unit and an external port, anantenna, a memory.

A sensor may allow the light source device 10 to measure parameters ofthe wound healing. These parameters may be for example the temperatureand the oxygenation level of the wound.

The microchip processor or the control unit may allow the light sourcedevice 10 to monitor the supply of electricity to the light emittingelement 12 to guarantee an optimum or desired blue light exposure. Forexample, the microchip processor or the control unit may control whetherthe light exposure is continuous or in pulses as well as the frequencyand the duration of the pulses depending on predetermined parameters orlive parameters such as values measured by a sensor of the light sourcedevice 10.

Furthermore, a communication unit may allow a user to recover data fromor transmit data to the light source device 10. For example, data may betransmitted to a smartphone or any other external device, notably anexternal device comprising a screen to display information useful to theuser. The communication unit may be configured for wireless transmissionor wired communication. In the case of a wired communication, the lightsource device 10 may comprise an external port connected to thecommunication unit for data transmission. Alternatively, thecommunication unit may be configured for both wireless and wiredcommunication.

Moreover, the light source device 10 may be included in a light sourceassembly (not shown) which comprises a product adapted to be in contactwith the skin or a wound formed on the skin. In this case, the lightsource device 10 is connected to the product for providing blue light toat least one skin cell of the skin or the wound.

For improving blue light effect, the light source assembly may beadapted to dispose the light emitting element 12 in a position whereinthe light emitting element 12 is facing the skin, preferably facing awound formed on the skin. In other words, the light source assembly isalso adapted to place the light emitting element on the facing page ofthe skin, preferably of the wound.

Furthermore, the light source device 10 may be configured so that bluelight is irradiated to the skin cells or the wound through the product.In doing so, the light source device 10 can irradiate the skin cells orthe wound without direct contact.

The light source assembly may be configured to allow setting orpredetermining of the distance between the light emitting element 12 andthe skin. Indeed, light intensity decreases with the square of thedistance from the source of the light. For example, light 1 meter awayfrom a source is four times as intense as light 2 meters from the samesource. Therefore, setting the distance between the light emittingelement 12 and the skin allows to monitor the irradiance and thus thefluence provided to the skin cells. The distance between the lightemitting element 12 and the skin may be predetermined from 0 to 50 mm,and preferably 0 to 20 mm in the case of a wound dressing for example.The distance between the light emitting element 12 and the skin may beof several centimeters in the case of a lamp used alone for example.

For setting or predetermining the distance between the light emittingelement 12 and the skin, the dimension of the product may be chosen topredetermine or set the distance between the light emitting element 12and the skin cells. Alternatively or in combination, the light sourceassembly may further comprise an adjustable element for adjusting thedistance between the light emitting element 12 and the skin.

The light source device 10 may also be configured so that the lightemitting element 12 may be selectively orientated to better target theskin cells to be irradiated. This orientation, or homogenization of thelight emitting element 12 allows the irradiation to be more adapted tothe geometry and the characteristics of a wound. These advantages becomeeven more significant when the light source device 10 comprises aplurality of light emitting elements 12. In this case, the lightemitting elements 12 may be orientated independently from each other towiden the irradiated area.

Furthermore, the light source device 10 may comprise a lens for focusingthe light onto the target cells or tissue to make the irradiation moreprecise.

The product may be one among a dressing, a strip, a compression means, aband-aid, a patch, a gel and a rigid or flexible support, a film-formingcomposition or similar. Furthermore, in an embodiment of the lightsource assembly, the product may be arranged so that the light emittingelement 12 is disposed on the interior of the product or in its inferioror superior surface. In this embodiment, the product adapted to contactthe skin or a wound is preferably a dressing. The dressing may compriseat least a hydrocolloid or an adhesive layer in contact with the skin orthe wound.

The light source assembly may be of any size or shape. In one particularembodiment, the assembly may be 8×8 cm in size. In another embodiment,the assembly may be 4×4 cm in size. The product may comprise an interiorlayer comprising a mesh material and a tissue gel. The mesh materialallows exudate from a wound to which the dressing is applied to beabsorbed into the dressing whilst allowing the tissue gel to flowthrough it so that it can be absorbed by a wound being treated.

For allowing the light source assembly to be reusable while avoidingrepetitive cleanup, the product may be disposable and interchangeable.In other words, the product may be configured to be separated from thelight source device 10 so that a same light source device 10 can be usedseveral times without the need of a cleanup. It also allows to changethe electronic elements included in the light source device 10 formaintenance, for example for recharging the battery.

Moreover, the effect of irradiation may at times be enhanced by theaddition of photosensitizer substances to the target cells or tissue.The concentration of such substance is substantially lower thanconcentrations used in photodynamic therapy. For example, a culture ofskin cells, such as fibroblasts or keratinocytes, may be supplementedwith small amounts of a photosensitizer substance, such ashematoporphyrin derivatives prior to light irradiation. Such substancesmay also be applied topically onto the skin prior to the light therapy.

A method for inducing or promoting growth and proliferation of cells isalso proposed. The method may be performed by any light source devicebut preferably by the light source device 10 and the light sourceassembly described above.

Cells or tissue are irradiated with a light at wavelengths between 435to 500 nm, and preferably having a dominant emission wavelengthcomprised between 450 and 460 nm. More particularly, the chosen dominantemission wavelength may be of 453 nm. The method may be performed invivo or in vitro. Cells or tissue may be in culture or directly from amammal tissue.

For inducing or promoting growth and proliferation of cells, cells ortissue may be irradiated to receive an effective fluence comprisedbetween 0.01 and 10 J/cm².

For inducing or promoting growth and proliferation of cells also, lightemitting source used in this method is in the range of about 0.05 mW/cm²to about 30 mW/cm², particularly 0.1 mW/cm² to 1 mW/cm², 1 mW/cm² toabout 2 mW/cm², 2 mW/cm² to 5 mW/cm², 5 mW/cm² to 10 mW/cm², 15 mW/cm²to 25 mW/cm² or any irradiance in a range bounded by, or between, any ofthese values. Preferably, the power density used to treat target cellsor target tissue is of 0.05 to 30 mW/cm², preferably of 15 to 25 mW/cm²,preferably of 20 to 25 mW/cm² and more particularly of 23 mW/cm².

More generally, the irradiation of blue light performed in this methodmay be set using all the different values of fluence, power intensityand time described above for the light source device 10 and the lightsource assembly.

This method allows to benefit from the same effects as described abovefor the light source device 10 and the light source assembly.Particularly, the present method allows to obtain the unexpectedtechnical effect of blue light consisting in inducing or promotinggrowth and proliferation of cells or tissue.

In particular, the method according to the invention is very useful forgrowth and proliferation of skin cells, such as cells of epidermisand/or dermis, such as keratinocytes or fibroblasts, preferablykeratinocytes.

The present invention also describes a light source device for use forthe in vivo growth and proliferation of cells or tissue, preferably skincells or tissue, such as keratinocytes or fibroblasts. Preferably, thelight source device is according to the present invention.

The present invention also describes a light source assembly containinga light source device for use for the in vivo growth and proliferationof cells or tissue, preferably skin cells or tissue, such askeratinocytes or fibroblasts. Preferably, the light source assembly isaccording to the present invention.

The invention will be illustrated further by the following examples:

Example 1: Effect of the Blue Light on the Growth and Proliferation ofKeratinocytes Cell Culture

Keratinocytes (HaCaT, Immortal Human Keratinocyte in Dulbecco's ModifiedEagle Medium, from CLS Company) were incubated in 96 multi-well plates.

The concentration of cells was about 2.5×10⁴ cells/well. 48 hours aftercell incubation, cells were washed with a phosphate buffered saline(PBS) solution.

Then, the wells containing the keratinocyte cells are treated by a bluelight.

Light Treatment

For the light treatment Lumileds Luxeon Rebel LXML-PR01-0275 fromKoninklijke Philips N.V. (Eindhoven/Netherlands) was used. The plateswere irradiated from a distance of 5 cm with a power density of 23mW/cm². The beam divergence was ±15° with a dominant emission wavelengthof 453 nm (blue light).

The keratinocyte wells were irradiated with different energy densities.

XTT Test (Measurement of the Keratinocyte Cell Proliferation)

The XTT Cell proliferation test is a well-known method for the skilledperson. For this test the Colorimetric Cell Viability Kit III fromPromoKine (Heidelberg/Germany) was used. For the test 50 μL oflabeling-mixture containing labeling reagent and electron couplingreagent was mixed with cell suspension where the XTT(2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide)is metabolized to water soluble formazan dye. Only viable cells have theability to metabolize, hence the formazan is used to directly quantifythe proliferation measured by spectrophotometric absorption withInfinite® 200 PRO microplate reader from Tecan Group AG.(Männedorf/Switzerland).

Results

The cell proliferation of keratinocytes is illustrated in the graph ofFIG. 2. The graph represents the “fold change” in function of thetransmitted fluence with blue light irradiation to the cells.

By “fold change”, it means the ratio of proliferation with blue light onthe proliferation with non-irradiated cells

In order to evaluate the attenuation or absorption of the light that canoccur if the skin tissue is irradiated with blue light, the loss oflight power has been evaluated through a lid (which reflects the light),a plate (culture wells which absorbs the light) and a medium culture (4mm of height for a volume of about 1.5 mL).

The energy density (fluence) effectively received after passing throughthe different elements listed above (lid, plate and medium culture) wasmeasured with a Power Meter® 843-R-USB from Newport Corporation. A lossof 45% has been observed.

The graph of FIG. 2 and the zoom of FIG. 3 shows that the exposure ofkeratinocytes to blue light (453 nm) with energy densities of less than18.5 J/cm², promotes or induces proliferation of keratinocytes whichwell shows that an irradiation with blue light can be used for thetreatment of wounds and injuries. On the contrary, the exposure ofkeratinocytes to blue light (453 nm) with energy densities higher than18.5 J/cm² inhibits proliferation of keratinocytes which and wouldtherefore not be suitable for the closure of wounds and injuries.

Example 2: Effect of the Blue Light on the Growth and Proliferation ofFibroblasts

The same protocol as the one used in example 1 was used by replacing thekeratinocyte cells by fibroblast cells: Normal Human Dermal Fibroblast(NHDF) in Dulbecco's Modified Eagle Medium (available from PromoCellCompany).

The cell proliferation of fibroblasts is illustrated in the graph ofFIG. 4. The graph represents the “fold change” in function of thetransmitted fluence with blue light irradiation to the cells.

The graph of FIG. 4 shows that the exposure of fibroblasts to blue light(453 nm) with energy densities of less than 18.5 J/cm² promotes orinduces proliferation of fibroblasts which well shows that anirradiation with blue light can be used for the treatment of wounds andinjuries. On the contrary, the exposure of fibroblasts to blue light(453 nm) with energy densities higher than 18.5 J/cm² inhibitsproliferation of fibroblasts which and would therefore not be suitablefor the closure of wounds and injuries.

1. A light source device comprising a light emitting element foremitting a blue light having a wavelength ranging from 435 to 500 nm,the light source device being configured to provide the blue light to atleast one cell at a transmitted fluence ranging from 0.01 to 18.5 J/cm²to promote or induce growth and proliferation of the cell and whereinthe light emitting element has a power density ranging from 0.05 to 30mW/cm².
 2. The light source device of claim 1, wherein the cell isselected from a skin cell.
 3. The light source device according to claim2, wherein the skin cells are keratinocytes or fibroblasts.
 4. The lightsource device of claim 1, wherein the dominant emission wavelengthranges from 450 to 490 nm.
 5. The light source device according to claim1, wherein the light source device is configured to provide the bluelight at a transmitted fluence so that the cell receives an effectivefluence ranging from 0.01 to 10 J/cm².
 6. The light source deviceaccording to claim 1, wherein the light emitting element has a powerdensity ranging from 20 to 25 mW/cm².
 7. The light source deviceaccording to claim 1, wherein said light emitting element comprises atleast one LED.
 8. The light source device according to claim 1, furthercomprising a power source providing electrical power to said lightemitting element.
 9. The light source device according to claim 8,wherein said power source is a battery.
 10. The light source deviceaccording to claim 1 further comprising at least one among a microchipprocessor, a control unit, a communication unit, an external port and asensor.
 11. A light source assembly comprising: a product adapted to bein contact with the skin or a wound; a light source device according toclaim 1 connected to the product for providing blue light to at leastone skin cell, preferably of the wound.
 12. The light source assemblyaccording to claim 11, wherein the product is one among a dressing, astrip, a compression means, a band-aid, a patch, a gel, a film-formingcomposition and a rigid or flexible support.
 13. The light sourceassembly according to claim 11, wherein the dressing comprises at leasta hydrocolloid or an adhesive layer in contact with the skin or thewound.
 14. The light source assembly according to claim 11, wherein thelight source assembly is adapted to dispose the light emitting elementin a position wherein the light emitting element is facing the skin.